Lateral Shift Makes a Ground-Plane Cloak Detectable

TL;DR

This paper demonstrates that ground-plane cloaks created from quasiconformal mapping induce a lateral shift in scattered waves, which can make cloaked objects detectable, challenging the cloak's invisibility effectiveness.

Contribution

The study reveals that non-anisotropic ground-plane cloaks cause a lateral shift in scattered waves, providing a new understanding of their limitations.

Findings

Lateral shift is comparable to the object's height.

Ray tracing shows a shift of about 0.15 units for a 0.2-unit bump.

Lateral shift can reveal the presence of the cloaked object.

Abstract

We examine the effectiveness of the ground-plane invisibility cloak generated from quasiconformal mapping of electromagnetic space. This cloak without anisotropy will generally lead to a lateral shift of the scattered wave, whose value is comparable to the height of the cloaked object, making the object detectable. This can be explained by the fact that the corresponding virtual space is thinner and wider than it should be. Ray tracing on a concrete model shows that for a bump with a maximum height of 0.2 units to be hidden, the lateral shift of a ray with 45 degree incidence is around 0.15 units.